1. Field of the Invention
This invention relates to magnetostriction detection type force sensors and, more particularly, to a magnetostriction detection type force sensor for detecting an external stress through use of a magnetostrictive element.
2. Description of the Prior Art
The conventional magnetostriction detection type force sensor 1, as shown in FIG. 2, has an accommodation case 2 in a cylindrical form serving also as a mounting substrate. The accommodation case 2 is inserted by a magnetostriction detecting coil 4 wounded around a coil bobbin 3. The coil bobbin 3 accommodates therein a magnetostrictive element 5 of a circular columnar form. Further, a cap member 7 with a spherical end face 6 is provided on an end of the magnetostrictive element 5.
In the conventional magnetostrictive detection type force sensor 1 constructed as above, the load force for example due to an object to be measured 8 is entirely applied onto the magnetostrictive element 5 through the cap member 7. Accordingly, the conventional force sensor 1 has a disadvantage of insufficiency in impact resistance. Meanwhile, there exists a gap between the accommodation case 2 having therein the magnetostrictive element 5 and the cap member 7, making it difficult to provide a sufficient magnetic path. The leak of magnetic flux may cause a problem of poor detection accuracy.
It is therefore a primary object of the present invention to provide a magnetostriction detection type force sensor which is excellent in impact resistance, small in size and high in accuracy.
A magnetostriction detection type sensor according to the present invention, comprises: a substrate formed by a magnetic member; a magnetostrictive element formed in a columnar form provided on the substrate; a magnetostriction detecting coil formed in a cylindrical form to coaxially receive the magnetostrictive element; and a housing case provided on the substrate in a manner covering the magnetostriction detecting coil and contacted with a tip surface of the magnetostrictive element.
Because the columnar magnetostrictive element and magnetostriction detecting coil inserted by this element provided on the magnetic member substrate are accommodated and protected within the housing case having the spherical end surface, the compression stress applied from an object to be measured is dispersed into the magnetostrictive element and substrate by the spherical end surface. Also, because a magnetic path is secured by the housing case, no leak of magnetic flux occurs.
According to the present invention, it is possible to reduce external forces to be applied to the magnetostrictive element. Thus, the resistance to load or impact is improved. Also, an ideal magnetic path is formed, sensitivity is improved, and surrounding magnetic fields are shielded from effecting upon. Furthermore, the sensor can be reduced in size.
The above described objects and other objects, features, aspects and advantages of the present invention will become more apparent from the following detailed description of the present invention when taken in conjunction with the accompanying drawings.